Module 2.1.6 - cell division Flashcards
What is cell division needed for?
Growth and repair
What are the 2 periods of a cell?
Cell growth and DNA replication (interphase)
What is M phase?
- period of cell division
- involves mitosis and cytokinesis
What separate growth stages is interphase divided into?
G1, S and G2
What are the stages of interphase?
- cell prepares to divide
- cell’s DNA is unraveled and replicated (to double its genetic info)
- organelles are replicated so has spare ones and its ATP content in increased
What is the cell cycle regulated by?
Checkpoints and occurring key points to make sure process is ok to continue
What is mitosis?
- continuous process but is described as a series of stage: prophase, metaphase, anaphase and telophase
- needed for growth and repair, some animals, plants and fungi use it to reproduce asexually
What is the structure of chromosomes in mitosis?
- chromosomes are made up of 2 strands joined by a centromere
- separate strands are called chromatids
- 2 strands on same chromosome are called sister chromatids
- 2 strands because each chromosome has already made an identical copy of itself during interphase
- when mitosis is over, chromatids end up as 1 strand chromosomes in new daughter cells
What are the stages of prophase?
- chromosomes condense (get shorter and fatter)
- centrioles (tiny bundles of protein) move to the opposite ends of cell, forming protein fibers across it called the spindle
- nuclear envelope (membrane around the nucleus) breaks down and chromosomes lie free in cytoplasm
What are the stages of metaphase?
- chromosomes line up along the middle of the cell (spindle equator) and become attached to spindle by their centromere
- at metaphase checkpoint, the cell checks all the chromosomes are attached to the spindle before mitosis can continue
What are the stages of anaphase?
- centromeres divide/move apart, separating each pair of sister chromatids
- spindles contract, pulling chromatids to opposite ends of the cell, centromere first
What are chromosomes made up of?
2 strands joined by a centromere
What are 2 separate strands of a chromosome called?
Chromatids
What are sister chromatids?
2 strands on same chromosome
What are the stages of mitosis?
Interphase - before mitosis
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis - after mitosis
What are the stages of telophase?
- chromatids reach opposite poles on the spindle
- uncoil and become long and thin again
- now called chromosomes again (not chromatids)
- nuclear envelope form around each group of chromosomes
What are the stages of cytokinesis?
- cytoplasm divides
- a cleavage furrow forms to divide the cells
- 2 genetically identical daughter cells are formed
Where does cytokinesis start and end?
Begins in anaphase and ends in telophase
Where does cytokinesis occur in animal cells?
By the furrowing of the cytoplasm
Where does cytokinesis occur in plant cells?
Is initiated with the formation of a cell plate in the middle of the cell
How do you investigate mitosis?
- treat the tips of growing roots in HCL and break them open carefully and spread a few on a microscope
- add a few drops of stain
- squash under a coverslip
- view under a microscope
What are egg and sperm cells called?
Gametes
What is a zygote?
2 gametes joined together at fertiliasation
What type of chromosomes do normal body cells have?
Diploid (contain 2 of each chromosome)
What are homologous chromosomes?
Pair of matching chromosomes that make up each pair, are same size and have same genes, although could have different versions of those genes
What type of chromosomes do gametes have?
Haploid (one copy of each chromosome)
What is meiosis?
- cell division that produces gametes
- cells formed are genetically different because each cells end up with a combination of chromosomes
What stage does meiosis begin with?
Interphase
What happens during interphase in meiosis?
The cells DNA unravels and replicates to produce double-armed chromosomes (sister chromatids)
What does meiosis involve?
2 divisions - M1 and M2
What is meiosis 1?
- after interphase the cell enters m1
- m1 is the reduction division (it halves the chromosome number)
What is differentiation?
Stem cells divide to become new cells, which then become specialised
What is meiosis 2?
- the daughter cells produced undergo prophase 2, metaphase 2, anaphase 2, telophase 2 and cytokinesis
- these are the same stages in meiosis 1, except with half the number of chromosomes
What is genetic variation?
- the difference that exists between individuals genetic material
- meiosis is important as it creates genetic variation
- during fertilisation, any egg can fuse with any sperm which also creates variation
- this means new individuals have a new mixture of alleles, making them genetically unique
What are stem cells?
Unspecialised cells that can develop into different types of cell
- all multicellular organisms have some form of stem cells
Where are stem cells found?
In bone marrow in human cells and in early embryos
What is differentiation in animals?
Adult stem cells are used to replace damaged cells
What are erythrocytes?
Red blood cells
What are neutrophils?
White blood cells
What is differentiation in plants?
- stem cells are used to make new roots and shoots
- can differentiate into various plant tissues
- stem cells are found in meristem
How are stem cells used for heart disease?
Make replacement heart cells to repair damages heart tissue as body can’t replace them
How are stem cells used for Alzheimer’s?
Nerve cells in brain die resulting in memory loss, sue stem cells to regrow healthy nerve cells in people with Alzheimer’s
How are stem cells used for Parkinson’s?
Causes loss of nerve cells in brain, these release chemical called dopamine which controls movement. transplanted stem cells may help regenerate dopamine-producing cells
What are specialised cells? (SC)
When cells differentiate they have a specific function, their structure is adapted to perform that function
What are red blood cells? (SC)
- carry oxygen in blood
- biconcave disc shape, provides large SA for gas exchange
- no nucleus, more room for haemoglobin
What are white blood cells? (SC)
- defend body against disease
- flexible shape, allows to engulf foreign pathogens
- many lysosomes in cytoplasm, contain digestive enzymes to break down engulfed particles
What are epithelial cells? (SC)
- cover surface of organs
- cells are joined by interlinking membranes
- in airways to waft particles away
- small intestine have microvilli, folds in cell membrane that increase SA
- squamous epithelia in lungs are very thin to allow efficient diffusion of gases
What are sperm cells? (SC)
- flagellum/tail, helps swim to egg cell
- many mitochondria, provide energy to swim
- acrosome, contains digestive enzymes to enable sperm to penetrate surface of egg
What are palisade mesophyll cells? (SC)
- where photosynthesis occurs
- contain many chloroplasts to absorb sunlight
- thin walls so CO2 can diffuse easily into cell
What are root hair cells? (SC)
- absorb water and mineral ions from soil
- large SA for absorption
- thin permeable cell wall, allows entry of water ions
- cytoplasm contains extra mitochondria, provide energy for active transport
What are guard cells? (SC)
- found in pairs with gap between for stoma (tiny pore for gas exchange)
- in light, guard cells take up water and become turgid
- thin outer walls and thick inner walls force them to bend outwards, opening stomata, allowing gas exchange for photosynthesis
What are tissues?
A group of cells that are specialised to work together o carry out a particular function
- can contain more than 1 cell type
What is squamous epithelium tissue?
- Single layer of flat cells lining a surface
- found in alveoli of lungs and provides thin exchange surface for substances to a diffuse across quickly
What is ciliated epithelium tissue?
- layer of cells covered in cilia
- found on surfaces where things need to be moved
e.g. in trachea where cilia waft mucus along
What is muscle tissue?
- made up of 2 bundles of elongate cells called muscle fibres
- 3 different types of muscle fibres : smooth, cardiac and skeletal
What are the 3 types of muscle tissue?
Smooth - found lining inside of stomach
Cardiac - found in heart
Skeletal - use to move
What is cartilage tissue?
- type of connective tissue found in joints
- shape and supports the ear, nose and windpipe
- formed when cells cells called chondroblasts secrete an extracellular matrix (jelly-like substance containing protein fibres) which they become trapped inside
What is xylem tissue?
- plant tissue which transports water around the plant and supports the plant
- hollow xylem vessels which are dead and living parenchyma cells
What is phloem tissue?
- transports sugar/sucrose around the plant
- arranged in tubes and is made up of sieve cells, companion cells and some ordinary plant cells
- each sieve cell has end walls with holes in them, so sap/sucrose can move easily through them, these end walls are called sieve plates
What are organs?
- group of different tissues that work together to perform a particular function
- have elastic connective tissue and vascular tissue (in blood cells)
e.g. lungs carry out gas exchange, contain squamous epithelium tissue in alveoli and ciliated epithelium in bronchi
What are organs in plants?
leaf - carry out gas exchange and photosynthesis, contains palisade tissue as well as epidermal tissue (to prevent water loss from leaf) and xylem and phloem tissues in the veins
What are organ systems?
Organs that work together to form organ systems, each has a particular function
What are 2 types of organ systems and what do they do?
Respiratory system - made up of all organs, tissues and cells involved in gas exchange
Circulatory system- made up of organs involved in blood supply, heart, veins, arteries and capillaries
